This invention relates to sheet stacking apparatus and more particularly to stacking apparatus in which sheets are successively inverted as they are deposited on the stacking platform. Stacking devices are known which can engage the leading edge of sheets moved along a path and divert the leading edge from the path so that the trailing portion of the document is pushed beyond the leading edge causing a sheet to be turned over. Such apparatus is exemplified by U.S. Pat. Nos. 2,649,303 and 2,904,334. The apparatus described by these patents has been devised to handle sheets of uniform size and having a relatively high degree of stiffness. Certain stacking requirements, however, demand the capability of being able to reliably invert sheets having the stiffness of punched card stock or tissue paper having a weight range of 140 No. (0.010 in. thickness) down to 10 No. (0.0018 in. thickness) or even greater range. In addition the stacker should have the capability of handling sheets of small, postal card-size to newspaper size, as encountered in handling printer output. A further requirement is that of permitting removal of a partial stack of sheets while the stacking operation continues uninterrupted.